1. Field of the Invention
This invention relates to a new and effective method of reinforcing a pair of opposed fastener tapes at and about their prospective bottom ends, to which a separable bottom stop assembly is to be molded, in manufacturing a continuous separable slide fastener chain by injection molding coupling element rows along confronting inner edges of the opposed fastener tapes being continuously supplied and a separable bottom stop assembly, which is composed of a pin member and a box member, on prospective bottom ends of the fastener tapes.
2. Description of the Related Art
Conventionally, in this type of slide fastener with a separable bottom stop assembly composed of a pin member and a box member, the fastener tape portions to which the separable bottom stop assembly is attached are reinforced to prevent such tape surfaces from being damaged.
To this end, it has been a common practice to stick reinforcement tape pieces such as synthetic resin film or woven fabric to the tape surfaces.
However, in this reinforcing method, as disclosed in, for example, Japanese Patent Laid-Open Publication No. HEI 2-153725, the reinforcement tape pieces are stuck to the fastener tapes by a reinforcement tape sticking machine, whereupon the resulting fastener tapes are fed to an injection molding machine independent of the reinforcement tape sticking machine. Then, in the injection molding machine, coupling element rows and a separable bottom stop are molded in order along the confronting inner edges of the reinforced fastener tapes.
Generally, between the reinforcement tape sticking machine and the injection molding machine, small holes are formed in the reinforced prospective bottom end portions in an attempt to secure an increased degree of peel strength of the separable bottom stop assembly on the fastener tapes. Further, another solution has been proposed by, for example, West German Patent Specification No. 635026, in which lattice ribs instead of the reinforcement tape pieces are molded on the fastener tapes simultaneously with the molding of the separable bottom stop assembly. Of course, reinforcement plates may be substituted for the lattice ribs.
In still another solution, as proposed by, for example, Japanese Utility Model Publication No. SHO 50-10888, the prospective bottom end portions of the opposed fastener tapes are treated by a synthetic resin process, whereupon generally E-shape ribs instead of the lattice ribs are molded on the synthetic resin treated portions.
However, according to the slide fastener chain manufacturing method disclosed in Japanese Patent Laid-Open Publication No. HEI 2-153725, the step of sticking the reinforcement tape pieces to the fastener tapes and the step of injection molding the separable bottom stop assembly are independent of each other and must take place continuously for a long period in timed relation to each other. Since the fastener tapes would be stretched or shrunk as they are subject to a predetermined amount of tension or are relaxed during the individual step, it is almost impossible to match the reinforcement tape sticking position with the separable bottom stop molding position.
According to the slide fastener chain manufacturing method disclosed in West German Patent Specification No. 635026, since the reinforced fastener tape end portions and the separable bottom stop assembly are molded simultaneously, no meticulous control is required for the above-mentioned positioning, thus improving the rate of production. However, assuming that the slide fastener manufactured by this method is sewn to a garment or the like, since the reinforced tape portion would have a thickness sharply larger than that of the fastener tape and would become rigid, it tends to be caught by the pressure foot of a sewing machine so that the sewing needle can be broken on many occasions. Yet if soft molding material could be used in an effort to avoid this breakage of the needle, the separable bottom stop would have been too soft for practical use.
The slide fastener chain manufacturing method disclosed in Japanese Utility Model Publication No. SHO 50-10888 has the same problems with those with the above-mentioned West German Patent and is difficult to secure positioning accuracy as well as the method disclosed in Japanese Patent Laid-Open Publication No. HEI 2-153725.